1. Field
The present disclosure relates to a fuel cell system and a method for controlling the fuel cell system.
2. Description of the Related Art
Fuel-cell vehicles include a fuel cell system serving as a power supply system. A fuel cell starts generating electricity if hydrogen gas serving as fuel gas and air serving as oxidant gas are supplied. To supply hydrogen gas to the fuel cell, an anode flow passage of the fuel cell has a hydrogen tank connected thereto via a hydrogen gas feed pipe. In addition, to supply air to the fuel cell, a cathode flow passage of the fuel cell has a compressor connected thereto via an air feed pipe. When the fuel cell system starts, the fuel cell system starts supplying hydrogen gas and air to start generating electricity using the fuel cell.
When the system is shut down and if oxygen remains in the cathode flow passage, the potential of the cathode of the fuel cell becomes high immediately after the system restarts and hydrogen is fed to an anode system. Accordingly, a solid polymer electrolyte membrane may be deteriorated. To solve such a problem, even when the fuel cell system is shut down, the fuel cell system causes the fuel cell to continue electrical generation and discharge using oxygen remaining in the cathode flow passage. In this manner, the fuel cell system causes the fuel cell to be inactive and, thereafter, completely stops (refer to, for example, Japanese Unexamined Patent Application Publication No. 2003-115317). In addition, in this discharge process, to further prevent oxygen from passing from the cathode side to the anode side, it is desirable that the remaining oxygen be consumed on the cathode side and extra hydrogen gas be supplied from the hydrogen tank to the anode side to maintain the pressure in the anode flow passage to be high.
In addition, in recent years, a technique of filling a hydrogen tank with hydrogen gas has been actively researched. For example, Japanese Unexamined Patent Application Publication No. 2011-33068 describes the following technique. That is, when a hydrogen filling apparatus in a hydrogen fueling station is connected to a fuel-cell vehicle in order to fill a hydrogen tank of the vehicle with hydrogen gas, the vehicle sends a data signal indicating, for example, the temperature and pressure of the tank, and the station fills the tank with the hydrogen gas in an optimum manner on the basis of the received data signal. Hereinafter, such a technique of filling the tank with the hydrogen gas under communication between a vehicle and a station is referred to as “communication fueling”.